Merge 3e2cbc016b ("Merge tag 'x86_splitlock_for_v5.19_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip") into android-mainline

Steps on the way to 5.19-rc1

Resolves merge conflicts in:
	kernel/fork.c

Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>
Change-Id: Ie6468a4dcebacddea949d1ad5dfbaddea481e033

arch/x86/include/asm/cpu.h

@@ -45,14 +45,12 @@ unsigned int x86_model(unsigned int sig);
 unsigned int x86_stepping(unsigned int sig);
 #ifdef CONFIG_CPU_SUP_INTEL
 extern void __init sld_setup(struct cpuinfo_x86 *c);
-extern void switch_to_sld(unsigned long tifn);
 extern bool handle_user_split_lock(struct pt_regs *regs, long error_code);
 extern bool handle_guest_split_lock(unsigned long ip);
 extern void handle_bus_lock(struct pt_regs *regs);
 u8 get_this_hybrid_cpu_type(void);
 #else
 static inline void __init sld_setup(struct cpuinfo_x86 *c) {}
-static inline void switch_to_sld(unsigned long tifn) {}
 static inline bool handle_user_split_lock(struct pt_regs *regs, long error_code)
 {
 	return false;

arch/x86/include/asm/thread_info.h

@@ -92,7 +92,6 @@ struct thread_info {
 #define TIF_NOCPUID		15	/* CPUID is not accessible in userland */
 #define TIF_NOTSC		16	/* TSC is not accessible in userland */
 #define TIF_NOTIFY_SIGNAL	17	/* signal notifications exist */
-#define TIF_SLD			18	/* Restore split lock detection on context switch */
 #define TIF_MEMDIE		20	/* is terminating due to OOM killer */
 #define TIF_POLLING_NRFLAG	21	/* idle is polling for TIF_NEED_RESCHED */
 #define TIF_IO_BITMAP		22	/* uses I/O bitmap */
@@ -116,7 +115,6 @@ struct thread_info {
 #define _TIF_NOCPUID		(1 << TIF_NOCPUID)
 #define _TIF_NOTSC		(1 << TIF_NOTSC)
 #define _TIF_NOTIFY_SIGNAL	(1 << TIF_NOTIFY_SIGNAL)
-#define _TIF_SLD		(1 << TIF_SLD)
 #define _TIF_POLLING_NRFLAG	(1 << TIF_POLLING_NRFLAG)
 #define _TIF_IO_BITMAP		(1 << TIF_IO_BITMAP)
 #define _TIF_SPEC_FORCE_UPDATE	(1 << TIF_SPEC_FORCE_UPDATE)
@@ -128,7 +126,7 @@ struct thread_info {
 /* flags to check in __switch_to() */
 #define _TIF_WORK_CTXSW_BASE					\
 	(_TIF_NOCPUID | _TIF_NOTSC | _TIF_BLOCKSTEP |		\
-	 _TIF_SSBD | _TIF_SPEC_FORCE_UPDATE | _TIF_SLD)
+	 _TIF_SSBD | _TIF_SPEC_FORCE_UPDATE)
 
 /*
  * Avoid calls to __switch_to_xtra() on UP as STIBP is not evaluated.

arch/x86/kernel/cpu/intel.c

@@ -7,10 +7,13 @@
 #include <linux/smp.h>
 #include <linux/sched.h>
 #include <linux/sched/clock.h>
+#include <linux/semaphore.h>
 #include <linux/thread_info.h>
 #include <linux/init.h>
 #include <linux/uaccess.h>
+#include <linux/workqueue.h>
 #include <linux/delay.h>
+#include <linux/cpuhotplug.h>
 
 #include <asm/cpufeature.h>
 #include <asm/msr.h>
@@ -999,6 +1002,8 @@ static const struct {
 
 static struct ratelimit_state bld_ratelimit;
 
+static DEFINE_SEMAPHORE(buslock_sem);
+
 static inline bool match_option(const char *arg, int arglen, const char *opt)
 {
 	int len = strlen(opt), ratelimit;
@@ -1109,18 +1114,52 @@ static void split_lock_init(void)
 		split_lock_verify_msr(sld_state != sld_off);
 }
 
+static void __split_lock_reenable(struct work_struct *work)
+{
+	sld_update_msr(true);
+	up(&buslock_sem);
+}
+
+/*
+ * If a CPU goes offline with pending delayed work to re-enable split lock
+ * detection then the delayed work will be executed on some other CPU. That
+ * handles releasing the buslock_sem, but because it executes on a
+ * different CPU probably won't re-enable split lock detection. This is a
+ * problem on HT systems since the sibling CPU on the same core may then be
+ * left running with split lock detection disabled.
+ *
+ * Unconditionally re-enable detection here.
+ */
+static int splitlock_cpu_offline(unsigned int cpu)
+{
+	sld_update_msr(true);
+
+	return 0;
+}
+
+static DECLARE_DELAYED_WORK(split_lock_reenable, __split_lock_reenable);
+
 static void split_lock_warn(unsigned long ip)
 {
-	pr_warn_ratelimited("#AC: %s/%d took a split_lock trap at address: 0x%lx\n",
-			    current->comm, current->pid, ip);
+	int cpu;
 
-	/*
-	 * Disable the split lock detection for this task so it can make
-	 * progress and set TIF_SLD so the detection is re-enabled via
-	 * switch_to_sld() when the task is scheduled out.
-	 */
+	if (!current->reported_split_lock)
+		pr_warn_ratelimited("#AC: %s/%d took a split_lock trap at address: 0x%lx\n",
+				    current->comm, current->pid, ip);
+	current->reported_split_lock = 1;
+
+	/* misery factor #1, sleep 10ms before trying to execute split lock */
+	if (msleep_interruptible(10) > 0)
+		return;
+	/* Misery factor #2, only allow one buslocked disabled core at a time */
+	if (down_interruptible(&buslock_sem) == -EINTR)
+		return;
+	cpu = get_cpu();
+	schedule_delayed_work_on(cpu, &split_lock_reenable, 2);
+
+	/* Disable split lock detection on this CPU to make progress */
 	sld_update_msr(false);
-	set_tsk_thread_flag(current, TIF_SLD);
+	put_cpu();
 }
 
 bool handle_guest_split_lock(unsigned long ip)
@@ -1193,18 +1232,6 @@ void handle_bus_lock(struct pt_regs *regs)
 	}
 }
 
-/*
- * This function is called only when switching between tasks with
- * different split-lock detection modes. It sets the MSR for the
- * mode of the new task. This is right most of the time, but since
- * the MSR is shared by hyperthreads on a physical core there can
- * be glitches when the two threads need different modes.
- */
-void switch_to_sld(unsigned long tifn)
-{
-	sld_update_msr(!(tifn & _TIF_SLD));
-}
-
 /*
  * Bits in the IA32_CORE_CAPABILITIES are not architectural, so they should
  * only be trusted if it is confirmed that a CPU model implements a
@@ -1230,6 +1257,7 @@ static const struct x86_cpu_id split_lock_cpu_ids[] __initconst = {
 	X86_MATCH_INTEL_FAM6_MODEL(SAPPHIRERAPIDS_X,	1),
 	X86_MATCH_INTEL_FAM6_MODEL(ALDERLAKE,		1),
 	X86_MATCH_INTEL_FAM6_MODEL(ALDERLAKE_L,		1),
+	X86_MATCH_INTEL_FAM6_MODEL(RAPTORLAKE,		1),
 	{}
 };
 
@@ -1274,10 +1302,14 @@ static void sld_state_show(void)
 		pr_info("disabled\n");
 		break;
 	case sld_warn:
-		if (boot_cpu_has(X86_FEATURE_SPLIT_LOCK_DETECT))
+		if (boot_cpu_has(X86_FEATURE_SPLIT_LOCK_DETECT)) {
 			pr_info("#AC: crashing the kernel on kernel split_locks and warning on user-space split_locks\n");
-		else if (boot_cpu_has(X86_FEATURE_BUS_LOCK_DETECT))
+			if (cpuhp_setup_state(CPUHP_AP_ONLINE_DYN,
+					      "x86/splitlock", NULL, splitlock_cpu_offline) < 0)
+				pr_warn("No splitlock CPU offline handler\n");
+		} else if (boot_cpu_has(X86_FEATURE_BUS_LOCK_DETECT)) {
 			pr_info("#DB: warning on user-space bus_locks\n");
+		}
 		break;
 	case sld_fatal:
 		if (boot_cpu_has(X86_FEATURE_SPLIT_LOCK_DETECT)) {

arch/x86/kernel/process.c

@@ -684,9 +684,6 @@ void __switch_to_xtra(struct task_struct *prev_p, struct task_struct *next_p)
 		/* Enforce MSR update to ensure consistent state */
 		__speculation_ctrl_update(~tifn, tifn);
 	}
-
-	if ((tifp ^ tifn) & _TIF_SLD)
-		switch_to_sld(tifn);
 }
 
 /*

include/linux/sched.h

@@ -942,6 +942,9 @@ struct task_struct {
 #ifdef CONFIG_IOMMU_SVA
 	unsigned			pasid_activated:1;
 #endif
+#ifdef	CONFIG_CPU_SUP_INTEL
+	unsigned			reported_split_lock:1;
+#endif
 
 	unsigned long			atomic_flags; /* Flags requiring atomic access. */
 

kernel/fork.c

@@ -1054,8 +1054,14 @@ static struct task_struct *dup_task_struct(struct task_struct *orig, int node)
 #ifdef CONFIG_MEMCG
 	tsk->active_memcg = NULL;
 #endif
+
+#ifdef CONFIG_CPU_SUP_INTEL
+	tsk->reported_split_lock = 0;
+#endif
+
 	memset(&tsk->android_vendor_data1, 0, sizeof(tsk->android_vendor_data1));
 	memset(&tsk->android_oem_data1, 0, sizeof(tsk->android_oem_data1));
+
 	return tsk;
 
 free_stack: